It is generally known from the prior art to package substances, such as for example drinks, creams, etc. in closed bags. The quality of the substance can be maintained by the hermetical seal from the outside world, which is provided by the wall of the bag. This wall may, for example, comprise single-layer or multilayer sheet material, in many cases comprising a plastic sheet. In order for it to be possible to dispense the substance back out of the bag, a connection between the outside world and the chamber in the bag has to be created in one way or another.
A known way of obtaining this connection is for a male element, for example a straw, to puncture the wall of the bag, so that the substance can be delivered from the bag via the straw. One example of this arrangement is described in U.S. Pat. No. 5,425,583. In this known bag, an opening is made in the wall as early as during production of the bag, and this opening is covered by a membrane of puncturable sheet which is attached to the wall of the bag.
In practice, the known bag has been found to have a number of drawbacks. For example, the bag is difficult to produce, since the puncturable membrane has to be fitted in a separate step and it is also necessary to ensure that the puncturable membrane is hermetically sealed to the wall of the bag. Furthermore, the puncturable membrane is not of the same quality as the rest of the wall of the bag, which detracts from the protection which the bag offers the substance. Another disadvantage is that when the membrane is punctured there is not a neat opening into which the straw fits in a sealed manner. In practice, leaks may easily occur along the outer side of the straw.
With this type of bag, there is also the risk, particularly in the case of relatively small bags, that not only the membrane but also the wall of the bag behind it will be punctured, resulting in an undesired leak in the bag. A further drawback is that when the membrane is punctured the substance will immediately emerge to the outside, certainly if the bag is being held firmly and squeezed.
Bags of other designs are also known from the prior art, in which a female element is secured in an opening in the wall of the bag or in a seam of the bag, with a bore which extends between the outside world and the chamber inside the bag. In these bags, there is also a plug for closing off the bore in the female element. A bag of this type is known, for example, from EP 0 749 358 and from WO 95/30856. A problem with these bags is that as long as the male element remains uncoupled to the female element, i.e. for example during transport and storage of the optionally filled bags, contamination may enter the bore of the female element from the outside.